This invention relates to finely atomizing fluid compositions to produce reproducible and homogeneous coatings in the nano-micrometer range on substrates. More particularly, this invention relates to a method and apparatus for controlling the particle formation and deposition process to form a biocompatible coating in-situ on a medical implant or a tissue surface of a mammal.
Fluid compositions comprising one or more therapeutic substances, one or more volatile solvents and film-forming components can be deposited on a medical device or a tissue. For example, coatings are often applied to medical implants, such as arterial stents, to improve the biocompatibility of the implants and/or deliver a therapeutic substance to a target surface. Other applications include coating a tissue surface of a living body with a therapeutic substance, such as a cell suspension of cultured epidermal cells, to enhance wound healing, adhering cells or depositing a therapeutic substance in the nasal cavity or lung to treat a disease.
Known processes generally do not ensure a controlled and reproducible film formation in the nano-micro range as well as precise control of the surface features resulting in decreased biocompatibility of the film. Problems include, among others, by excessive amounts of residual solvents and other additives, decreased potency of sensitive therapeutic substances, insufficient control of drug load and drug release, uneven distribution of therapeutic substances and/or poor control of the coating morphology.